How to perform surface boundary integration in elasticity fem?

This is a basic question regard to elsticity fem.

How to compute traction boundary integration numerically in elasticity fem under general situation? That is:

\int_{\Gamma} [N][t] d\Gamma,   here [N] is shape function and [t] is surface traction

 My E-mail: shengxu.xia@yahoo.com

Thanks a lot